Coronary arterial dominance

Coronary arterial dominance is defined by the vessel which gives rise to the posterior descending artery (PDA), which supplies the myocardium of the inferior 1/3rd of the interventricular septum.

Most hearts (80-85%) are right dominant where the PDA is supplied by the RCA. The remaining 15-20% of hearts are roughly equally divided between left dominant and codominant. The strict definition of codominance can vary depending of which modality one uses to assess the coronary arteries (coronary angiography or CTCA) but is not overly important. Regardless, in left dominant hearts the PDA is supplied by the LCx wrapping around the left atrioventricular groove or less commonly the LAD coursing around the apex of the heart. In a codominant heart a single or duplicated PDA is supplied by branches of both the RCA and LAD or LCx.

Although the RCA is the dominant vessel in most hearts, it is important to consider that it is usually the LCA that supplies the majority of the left ventricular myocardium as well as the anterior and mid 2/3rds of the interventricular septum.

Clinical relevance

Dominance has important implications in myocardial ischaemia and infarction, imaging of the coronary arteries (CTCA and invasive coronary angiography) and the planning for coronary artery bypass grafting.